1. Field of the Invention
The present invention relates in general to computers, and more particularly to a system and method of optimized data migration with a support processor in storage systems.
2. Description of the Prior Art
Data storage systems are used to store information provided by one or more host computer systems. Such data storage systems receive requests to write information to a plurality of data storage devices and requests to retrieve information from that plurality of data storage devices. It is known in the art to configure the plurality of data storage devices into two or more storage arrays.
Storage systems provide high availability and reliability characteristics through architectural design implementations that provide redundancy to protect the system. Fault tolerance is achieved in systems via redundant fault tolerant hardware designs and user data is stored in arrays of storage devices configured in a redundant array of independent disks (RAID) scheme. Traditional RAID schemes (RAID levels 1, 2, 3, 4, 5, 10 [0+1, 1+0]) provide a single level of redundant protection and are tolerant of a single device failure prior to being exposed to data loss from an additional failure. Online RAID array repair, generally known as “hot sparing”, restores RAID array redundancy following a failure of a storage device.
There are scenarios where an array repair action (sparing activity) results in a less-than-optimum configuration of the RAID array. In some cases, it may be desirable to replace/migrate a RAID array member storage device of a configuration. Examples of such cases include a RAID array repair action (sparing activity) resulting in an intermix of storage device types with a less-than-optimal configuration. The intermix of storage devices can include such non-aligned characteristics as a device capacity mismatch, device performance characteristics, including speed (RPM) and interface rate, device reliability characteristics such as enterprise class, near-line class, and desktop class, and storage device network position. In addition to the foregoing characteristics, a multi-storage device service boundary may result in data migration to create an acceptable service boundary.
To migrate the data from an active RAID array member (source) to a new target device, it is desirable to perform some sort of copying activity to migrate the data from source to target rather than forcing the RAID array into a rebuild of the device that is desired to be migrated to the new device. Prior art includes the RAID controller forming a RAID 1 relationship between the source and target device and performing a mirror rebuild to synchronize the data between the source and target devices. This method requires significant RAID controller and storage device fabric resources to complete. The resources consumed by the RAID controller and storage device network fabric impact the overall system performance during the duration of a particular activity.